An investigation is underway into the cause of a two-alarm blaze that tore through a wood supply business in Mapunapuna Thursday night. The fire broke out shortly before 7 p.m. on Kilihau Street. Flames shooting up from contractor supply company Rinell Wood System Inc. could be seen from drivers on the H-1 Freeway. The fire was extinguished about an hour later. No injuries were reported. The cause of the fire and the damage estimate is under investigation.